The emission of carbon dioxide gas into the atmosphere from industrial sources such as power plants is now considered to be a principal cause of the “greenhouse effect”, which contributes to global climate change. In response, efforts are underway to reduce carbon dioxide emissions. Many different processes have been developed to accomplish this task. Examples include polymer and inorganic membrane permeation; removal of carbon dioxide by adsorbents such as molecular sieves; cryogenic separation; and scrubbing with a solvent that is chemically reactive with carbon dioxide, or which has a physical affinity for the gas.
Most carbon capture techniques, such as those used in acid gas removal systems or low-pressure carbon dioxide absorbers in gasification units, use dilute aqueous solutions operated at low temperatures, of about 40° F. or below, to remove carbon dioxide from flue gas streams, e.g. exhaust gas produced at power plants, to produce a stream of high purity carbon dioxide. The high purity carbon dioxide product is then used in enhanced oil recovery (EOR), gasification applications, or sequestered in saline aquifers.
Recently, a new process for carbon dioxide recovery using an aminosilicone solvent has been developed, as disclosed in International Application Publication No. WO 2013/028391, U.S. Patent Application Publication No. 2013/0202517, and in Perry et al., Aminosilicone Solvents for CO2 Capture, ChemSusChem Energy & Materials, 3(8): 919-930 (2010) (“Perry et al.”). Typical carbon dioxide recovery using an aminosilicone solvent involves contacting an exhaust gas stream containing carbon dioxide (such as a gas turbine exhaust) with a lean aminosilicone solvent that is fed to an absorption apparatus. The lean aminosilicone solvent reacts with carbon dioxide and forms rich aminosilicone solvent. Desorption of the carbon dioxide from aminosilicone solvent occurs in a desorber apparatus, which is a high pressure Continuous Stirred Tank Reactor (CSTR). The desorption process generates a carbon dioxide-rich vapor stream, which leaves the desorber apparatus. However, this vapor stream also contains significant amounts of valuable aminosilicone solvent, such as 1,5-bis-(3-aminopropyl)hexamethyl-trisiloxane (GAP-1) and GAP-1 carbamate. Because loss of the aminosilicone solvent with the vapor stream is wasteful, recovery of the aminosilicone solvent from the vapor stream is desired.